Regenerative pump

ABSTRACT

Side-channel centrifugal pump in sectional construction, the stage packs of which comprise a suction connector (6), a pressure connector (7), a vane (10) and a casing shell element (8, 9). In order to reduce the structural complexity, the suction and pressure connectors (6, 7) are formed as sheet-metal parts and are disposed in an annular casing shell element (8, 9). The centering of the suction and pressure connectors (6, 7) is expediently effected from the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the national stage of International Application Ser. No.PCT/EP96/03806 filed Aug. 29, 1996.

BACKGROUND OF THE INVENTION

In side-channel pumps, it is necessary to maintain a tight play betweenthe vane and the surrounding casing parts. If the gap becomes too large,the leakage flows within the pump increase and pumping capacity andeffectiveness decline. Since the vanes must also be prevented, as far aspossible, from running up against the casing parts, this means thatthose casing parts of the pump which enclose the vane, and the vaneitself, must be accurately centred one to another and must be setperpendicular to the shaft. Finally, care should be taken inside-channel pumps to ensure that both the vane and the casing exhibithigh strength characteristics, since side-channel pumps, in contrast tonormal-intake pumps, can achieve many times higher pressures given equalpump dimensions and rotation speeds. This is particularly true ofsectional pumps having a plurality of stages, in which very highpressures are obtained with just a relatively low number of stages. Allthese aspects have hitherto resulted in the casing parts which enclosethe vane generally being constructed as metallic castings in which theinteracting faces are worked with tight production tolerances. Althougha pump of similar type, namely a peripheral pump, has been disclosed(GB-A 968 511), in which all pump casing parts are formed from sheetmetal, this is only conceivable where the requirements in terms oftrueness of running and efficiency are very low.

SUMMARY OF THE INVENTION

The object of the invention is to reduce the production complexity inside-channel centrifugal pumps of the type stated in the introduction,whilst maintaining a high level of efficiency. The solution according tothe invention consists in the suction and pressure connectors of atleast one stage pack being formed as sheet-metal parts and beingdisposed in an annular casing shell element.

The fact that the casing parts enclosing the vane are deep-drawn andpunched as simple sheet-metal parts or are spatially formed in a similarfashion and the casing shell elements which reach over them areconfigured as simple annular parts means that the structural complexityis very low. The invention is based on the recognition that thedimensional accuracy which is now available for sheet-metal parts bydeformation technology is sufficient, under certain preconditions, forsuch sheet-metal parts to be used as casing parts for side-channelpumps. The precondition for this is, however, that the sheet-metal partsshould be of such simple design that a flat plate can be used as theoriginal blank, which is then deep-drawn in the desired manner.

Although it is known (EP-A 588 258), in a normal-intake centrifugalpump, to provide a disc-shaped annular element of a stepped casing packmade from formed sheet-metal, there are no fundamental accuracyrequirements placed upon this part, whereas those inner casing partswhich interact with the impeller are traditionally configured ascastings.

Furthermore, in a normal-intake centrifugal pump (DE-A 36 29 123) onwhich no fundamental efficiency requirements are placed and in which thedistributor of the individual pump stages is not therefore particularlymatched in shape to the impeller, it is known to make this distributorfrom sheet-metal; yet, because of the different accuracy requirements,this cannot be a model for side-channel centrifugal pumps.

The casing shell elements of successive stages can be centred at theends in a known fashion one to another and in relation to the end casingparts. They can also centre the suction and pressure connectors at theirouter periphery. According to the invention, however, an embodiment ispreferred in which the suction and pressure connectors in the casingshell elements exhibit radial play and are centred from the shaft. Theradial play between the suction and pressure connectors and the casingshell elements is expediently only present during assembly, whereas,once assembly is completed and they have been centred by the shaft, thesuction and pressure connectors are firmly clamped between the casingshell elements.

In an advantageous embodiment, the centering from the shaft is realizedby virtue of the fact that in each pressure connector there is disposeda bearing bush carrier, which is centred on the outer periphery of anassigned bearing bush seated on the shaft. The suction connector canthen be centred in each case by the adjacent pressure connector of thepreceding stage, in that its inner bore reaches over the bearing bushcarrier or bearing bush of the latter. Just like the vane itself, thecasing parts enclosing the vane are therefore centred by the shaft. Theshaft, in turn, is centred in relation to the outer casing. The bearingbush carriers can be moulded onto the pressure connectors by drawing oranother non-cutting deformation process; they can also however be weldedto them. With a view to fitting accuracy, they are expediently workedexternally and internally. The latter also applies to the centering boreof the suction connector, whereas the outer diameters of the suction andpressure connectors do not generally need to be worked.

The gap accuracy between the suction and pressure connectors on the onehand and the vane on the other hand, where these parts are formed fromsheet metal, can be promoted by the fact that, according to theinvention, the suction connector is configured wholly, or at least inits region interacting with the vane, as a flat plate. This casing part,which interacts with the vane over a particularly large area, isconsequently not prone to distortion. The entire radial outer boundaryof the delivery chamber is assigned here to the pressure connector,which is anyway subject to greater deformation and interacts with thevane with a smaller surface component. This offers firstly the advantagethat those faces of the connectors for which relatively large productiontolerances have to be expected interact with the vane to a lesserextent, so that under the given deformation conditions a vane play isattained which is as low as possible in overall terms.

A further advantage derives from the following association. Since thepressure casing part is not sharp-edged but passes in curved progressionfrom its peripheral surface into its flange, which is clamped betweenthe casing shell elements, a peripheral groove is formed in the regionof this curvature on the outer periphery of the wheel, which peripheralgroove is undesirable in principle and is bounded in cross-section bythis curvature and the suction connector. If, as usual, the radiallyouter boundary of the delivery chamber were to be assigned partly to thesuction connector and partly to the pressure connector, this groovewould be twice as large due to dual-sided curvature; accordingly, theleakage flow would be at least twice as great. The fact that the workchamber is bounded in the radially outward direction solely by thepressure connector, whilst the suction connector is flat, means thatthis leakage current is minimized. Although even this leakage flow caneven be prevented by machine-working the inner diameter of the pressureconnector, the invention seeks specifically to avoid this complexityand, for this reason, preferably does without it.

The sealing against the ambient atmosphere is expediently executedbetween adjacent casing shell elements, since their relatively thickwall dimensions are able to accommodate an O-ring seal, for example,without difficulty.

A simple and effective option for ensuring the spacings between theindividual stage packs can be achieved by the suction and pressureconnectors being axially fixed between the casing shell elements.

The associated suction and pressure connectors should be fixed inrelation to one another in the peripheral direction as well. Accordingto the invention, this is most easily realized by punching a recess intothe periphery of one of these parts, a projection of the other partengaging into this recess. This arrangement is expediently situatedwithin the marginal region of the suction and pressure connectors, whichregion lies between the end faces of adjacent casing shell elements. Forexample, a narrow cut-out can be punched in the periphery of the suctionconnector, into which cut-out there engages a lug which is notched outfrom the periphery of the pressure connector. These moulded elementsrequire no additional manufacturing effort, since they can be fittedsimultaneously with the other shaping procedure for the sheet-metalparts.

Where particularly high requirements are placed on the seal-tightness ofthe pump, according to the invention the whole of the stage packs can bedisposed in a surrounding pot, which is expediently also provided withsuction and pressure sockets, only this pot needing to be sealed againstthe atmosphere. A single sealing point on the casing will generallysuffice for this purpose. Any leaks between the stages and the interiorof the surrounding pot can generally be neglected, so that there is noneed for a special seal between the casing shell elements. Whererequired, such seals can however additionally be fitted.

The casing shell elements of the stage packs can be axially braced usingthe fastening elements of the surrounding pot.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below with reference to thedrawing, which depicts advantageous illustrative embodiments and inwhich:

FIG. 1 shows a cross-section through a first embodiment,

FIG. 2 shows an enlarged detail of FIG. 1 and

FIG. 3 shows a second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The casing of the pump represented in FIG. 1 is closed at the ends bythe pump suction casing 2 with suction sockets 4 and by the pumppressure casing 3 with pressure sockets 5. Connected to these arebearing brackets 13 with ball bearings 14, which support and centre theshaft 1. The suction and pressure casings 2, 3 also contain the shaftseals 19.

Clamped between the pump suction and pressure casings 2, 3 arecylindrical casing shell elements 8, which are centred with one anotherand with the pump pressure casing 3 directly and with the pump suctioncasing 2 via an additional centering ring 9 and are mutually sealed byO-rings 15.

Clamped between the casing shell elements 8, and between a casing shellelement 8 and the ring 9, there are respectively the margins of asuction connector 6 and of a pressure connector 7. They are therebyaxially positioned and fixed. They form, together with the associatedvane 10 and a casing shell element 8, a respective stage pack.

The outer margins of the suction and pressure connectors 6, 7 areclamped between end faces of the casing shell elements 8, 9 and, as longas this clamping is not yet effective during assembly, enjoy playrelative to the associated inner diameter of the casing shell elements.The respectively outermost suction and pressure connectors are centredby the hub parts of the suction and pressure casings 2, 3. The suctionand pressure connectors 6, 7 located therebetween are centred from theshaft 1 via a bearing bush 12. For this purpose, the pressure connectorof the stage represented on the left in the drawing is welded to abearing bush carrier 11, which interacts in a centering fashion with theouter periphery of the bearing bush 12. The inner diameter of thesuction connector 6 of the stage represented on the right is worked suchthat it fits the outer diameter of the bearing bush carrier 11 and iscentred by the latter.

The pressure connectors 7 are formed such that they fully form the sidechannel 16 and the radially outer boundary 17 of the delivery chamber.In contrast to this, the suction connector 6 is configured wholly, oronly with the exception of its radially innermost region which does notinteract with the vane, as a flat plate and is therefore not subject todistortion. It is additionally envisaged that the suction connector 6consists of relatively thick material (for example, 3 mm) so as to offerparticularly good preconditions for a consistently flat design. Thepressure connector 7 can be somewhat thinner by comparison (for example2 mm).

At the point 18 at which the two connectors 6, 7 meet at the outerperiphery of the work chamber, the curved transition of the cylindricalpart 17 of the pressure connector 7 into its radial flange region givesrise to a groove, which is particularly clearly discernible in theenlarged representation of FIG. 2 and which is bounded in a roughlytriangular shape by the flat surface of the suction connector and thecurved surface of the pressure connector and in which an undesirablereturn-flow of pumping medium from cell to cell is possible. If, as isotherwise usual, the radially outer boundary of the delivery chamberwere to be disposed in the vane region on the suction connector 6 and inthe side-channel region on the pressure connector 7, then thecross-section of this groove would double, since the curved boundarywould then appear on both sides. This is prevented--as a furtheradvantage--by the flat design of the suction connector 6.

Those parts of the second embodiment, represented in FIG. 3, which areidentical with or correspond to the above-described parts of the firstembodiment are provided with identical reference numbers.

The pot casing 32 is provided both with suction sockets 4 and pressuresockets 5. It forms the pump casing jointly with the casing cover 33,which contains the shaft seal 19. The casing is held by the bearingcarrier 13 with foot 34 and ball bearings 14, which hold the shaft 1 insuspension-mounting.

The outer casing 32, 33 is axially clamped together by fasteningelements 24. The casing shell elements 8 and the annular elements 9,which latter are provided in this example in respect of each stage pack,as well as a transfer ring 22, are thereby axially clamped together.Seals between the casing shell elements 8, 9 and the adjoining casingparts are not provided. The outward sealing is provided here solely byan O-ring 15 between the outer casing parts 32, 33.

Emanating from the suction socket 4, the medium flows through the pumpin the axial direction through the stages and into the pressure chamber20 of the last side-channel stage. From here it flows through openings21 in the transfer ring 22, which assists in the centering and axialfixation of the casing shell elements, into the space 23 between the pot32 and the casing shell 8, 9 and finally leaves the pump through thepressure socket 5.

For an explanation of the suction and pressure connectors 6, 7 and theirdetails, reference is made to the description of the first illustrativeembodiment.

The casing shell elements are constructed many times thicker than thesheet-metal parts 6, 7.

What is claimed is:
 1. A multistage side-channel centrifugal pumpcomprising:a plurality of stage packs, each said stage pack including asuction connector, a pressure connector, a vane and at least one annularcasing shell element having axially opposed end faces, and a shaft,wherein said suction and pressure connectors are formed as sheet-metalparts having outer margins and said suction and pressure connectors aredisposed with said outer margins between the end faces of said annularcasing shell elements and at least one said suction connector and atleast one said pressure connector have radial play within said annularcasing shell elements and are centered from said shaft.
 2. Theside-channel centrifugal pump according to claim 1, characterized inthat in said at least one pressure connector there is disposed a bearingbush carrier with centering on the outer periphery of a bearing bush andin that an inner bore of said at least one suction connector is centeredon the bearing bush carrier of the preceding stage.
 3. The side-channelcentrifugal pump according to claim 1, characterized in that in thepressure connector there is disposed a side channel, a pass-throughopening for the pumping medium and a radial outer boundary of a deliverychamber, and the suction connector is configured, in its regioninteracting with the vane, as a flat plate.
 4. The side-channelcentrifugal pump according to claim 1, characterized in that the sealingof the stage packs against the ambient atmosphere is disposed at anouter margin of said suction connector and said pressure connectorbetween the annular casing shell elements.
 5. The side-channelcentrifugal pump according to claim 1, characterized in that the suctionand pressure connectors are axially fixed between the annular casingshell elements.
 6. The side-channel centrifugal pump according to claim1, characterized in that the suction and pressure connectors are fixedrelative to each other in the peripheral direction by tongue-and-grooveconnection.
 7. The side-channel centrifugal pump according to claim 1,characterized in that the stage packs are disposed in a surrounding pothaving suction and pressure sockets and the annular casing shellelements are of seal free configuration.
 8. The side-channel centrifugalpump according to claim 7, characterized in that the annular casingshell elements of the stage packs are clamped together by at least onefastening element of the surrounding pot.
 9. The side-channelcentrifugal pump of claim 1, wherein said at least one pressureconnector includes a bearing bush carrier centered on the outerperiphery of a bearing bush and an inner bore of said at least onesuction connector is centered on the bearing bush of the precedingstage.
 10. A multistage side-channel centrifugal pump comprising:acasing including a pump suction casing with at least one suction socket,said suction casing including a bearing bracket including a bearing forsupporting and centering one end of a shaft, an axially spaced pumppressure casing with at least one pressure socket, said pressure casingincluding a bearing bracket including a bearing for supporting andcentering an axially opposed end of said shaft and at least one annularcasing shell element centered from said suction casing, said casingshell element having oppositely disposed end faces, and a plurality ofstage packs, each stage pack including a sheet-metal suction connector,a sheet-metal pressure connector and a vane centered on and mounted tosaid shaft, said connectors having outer margins, wherein at least onesaid suction connector and at least one said pressure connector havecentering means interactive with said shaft and are disposed with radialplay in the casing shell element with said outer margins positionedbetween said end faces and are centered from the shaft and clampedbetween said end faces.
 11. The multistage side-channel centrifugal pumpof claim 10, wherein said at least one pressure connector comprises abearing bush carrier centered on the outer periphery of a bearing bushand said at least one suction connector comprises an inner bore centeredon said bearing bush carrier.
 12. The multistage side-channelcentrifugal pump of claim 10, wherein said at least one pressureconnector comprises a bearing bush carrier centered on the outerperiphery of a bearing bush and said at least one suction connectorcomprises an inner bore centered on said bearing bush.
 13. Themultistage side-channel centrifugal pump of claim 10, wherein saidpressure connector comprises a pass-through opening for the pumpingmedium and a radial outer boundary of a delivery chamber and saidsuction connector is configured, in its region interacting with thevane, as a flat plate.
 14. The multistage side-channel centrifugal pumpof claim 10, wherein the sealing of the inside of the pump against theambient atmosphere is disposed in the region of said shell casingelements.
 15. The multistage side-channel centrifugal pump of claim 10,wherein said suction and pressure connectors are axially fixed betweensaid casing shell elements.
 16. A method for assembling a pump of themultistage side-channel centrifugal type comprising a shaft, a casingincluding a pump suction casing, said suction casing including a bearingbracket including a bearing for supporting and centering one end of saidshaft, an axially spaced pump pressure casing, said pressure casingincluding a bearing bracket including a bearing for supporting andcentering an axially opposed end of said shaft and a plurality ofannular casing shell elements having oppositely disposed end faces, anda plurality of stage packs, each said stage pack including a suctionconnector, a pressure connector and a vane, said suction and pressureconnectors having outer margins, at least one said suction connector andat least one said pressure connector having centering means interactivewith said shaft, said assembly method comprising:positioning said atleast one pressure connector and said at least one suction connector onsaid shaft with said outer margins between said end faces whereby saidat least one pressure connector and said at least one suction connectorare centered from said shaft and have radial play relative to saidannular shell casing elements, and bracing said annular casing shellelements in an axial direction whereby said at least one pressureconnector and said at least one suction connector are fixed relative tosaid annular casing shell elements.